The present invention is directed to electrical filters, and more particularly to low pass filters for high power applications.
Electrical filters find use in radio frequency transmission paths to block unwanted frequencies. With reference to FIGS. 1 and 2, an electrical filter 10 of the prior art may include a series of alternating capacitive elements 12 and inductive elements 14 in an electrically conductive tube 16. The capacitive elements 12 are separated from the tube 16 by a dielectric 18, and the inductive elements 14 are surrounded by air. The elements 12 and 14 are electrically connected to form a first electrical path 20 therethrough. The tube 16 forms a second electrical path 22, with the capacitive elements 12 forming parallel shunts to the second path 20. See, for example, U.S. Pat. No. 4,680,560 issued Jul. 14, 1967 to Yorita, et al.
It is desirable to reduce the size of electrical filters while maintaining their operational capability. However, such filters tend to generate heat, and size reductions exacerbate the problem of conducting away heat generated by the capacitive and inductive elements inside the filter. Filters of reduced size are not adaptable to high power applications (up to about 4000 Watts), and filters capable of handling high power are larger than desired.
Accordingly, it is an object of the present invention to provide a novel electric filter that obviates the problems of the prior art.
It is another object of the present invention to provide a novel electric filter that is small, yet is able to conduct heat from the heat generating components inside the filter so that the filter can operate at high power.
It is yet another object of the present invention to provide a novel electric filter that includes a thermally conductive dielectric around the inductive elements that is in contact with a thermally conductive dielectric sleeve around all the elements and with adjacent capacitive elements to improve heat conduction from the inductive elements.
It is still another object of the present invention to provide a novel electric filter in which air separates the filter's outer electrically conductive tube from an internal dielectric sleeve that surrounds the filter elements, thereby forming two series-connected capacitors within each capacitive element to improve performance in a small filter.
It is a further object of the present invention to provide a novel electric filter that includes a thermally conductive dielectric sleeve around the filter elements that is separated from the outer conductor by an air-filled gap, the sleeve and the outer conductor touching to improve heat conduction from the interior of the filter.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of preferred embodiments.